Forming a three-dimensional pattern on a substrate (e.g. a semiconductor wafer) by using a photolithography technique is widely practiced these days in performing fine processing of the substrate. For example, a process for forming a resist pattern on a semiconductor wafer comprises forming a resist film on a surface of the semiconductor wafer, exposing the resist film along a predetermined pattern, and developing the resist film after exposure by reacting it with a developer.
A variety of developing techniques have heretofore been developed. For example, patent document 1 discloses a developing method which involves forming a puddle of a developer on a stationary substrate. A long nozzle having an ejection orifice(s) is used for the formation of the puddle: the developer is applied onto the entire surface of the resist film on the substrate by ejecting the developer from the ejection orifice(s) while moving the nozzle from one end to the opposite end of the substrate. For convenience sake, such a developing method is herein referred to as a “stationary developing method”.
Patent document 2 discloses a developing method in which a developer is supplied onto a rotating substrate. The developer is ejected toward the substrate from an ejection orifice of a nozzle while moving the nozzle in the radial direction of the substrate. A liquid film of the developer is formed on a resist film by the action of centrifugal force due to the rotation of the substrate and by the movement of the developer supply position. For convenience sake, such a developing method, in which a developer is supplied onto a rotating substrate, is herein referred to as a “rotary developing method”. Patent document 3 discloses an exemplary developing method which is classified as a rotary developing method. In particular, the method of patent document 3 uses a nozzle having a lower-end surface and disposed such that the lower-end surfaces faces an area of a wafer, the area including the axis of rotation of the wafer. A liquid is supplied from the nozzle onto the rotating wafer while the gap between the wafer and the lower-end surface of the nozzle is kept filled with the liquid. The liquid spreads outwardly on the wafer due to centrifugal force.